The potential energy (PE) of an object at height \( h \) can be calculated using the formula:
\[ PE = mgh \]
where:
- \( m \) is the mass of the object (in kilograms),
- \( g \) is the acceleration due to gravity (approximately \( 9.81 , \text{m/s}^2 \) on Earth),
- \( h \) is the height above ground level (in meters).
For the water tank:
- \( m = 38,000 , \text{kg} \)
- \( g = 9.81 , \text{m/s}^2 \)
- \( h = 58 , \text{m} \)
Now, substituting the values into the formula:
\[ PE = 38,000 , \text{kg} \times 9.81 , \text{m/s}^2 \times 58 , \text{m} \]
Calculating this step-by-step:
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Calculating the force due to gravity: \[ 38,000 \times 9.81 = 372,780 , \text{N} \]
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Now, calculating the potential energy: \[ PE = 372,780 , \text{N} \times 58 , \text{m} = 21,631,440 , \text{J} \]
Rounding up to appropriate significant figures based on the given choices, it appears that \( 21,599,200 , \text{J} \) is the closest match.
Thus, the potential energy of the water tank is \( \boxed{21,599,200 , \text{J}} \).